This invention relates to a process for the production of diethanolamine from monoethanolamine and ethylene oxide.
The production of ethanolamines is well known. Typically, ethylene oxide (EO) is reacted with aqueous ammonia, which produces a mixture of monomethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), and a variety of co-product impurities such as ethylene glycol. It is also well known that the distribution of MEA, DEA, and TEA varies depending on the ammonia/EO ratio. In general, a low ammonia/EO ratio results in a higher TEA level and high ammonia/EO ratio results in a higher level of MEA in the distribution product. DEA production, however, is normally limited to a maximum of about 35% due to the inherent reaction kinetics of the addition reactions. A graph which depicts the varying amounts of ethanolamines depending on ammonia/EO ratios can be found in British Patent 763,932 from 1952.
However, there is a growing need for DEA in certain markets. A process which overcomes the inherent difficulties discussed above, which achieves higher yields of DEA, would therefore be highly desirable.
Also known is reactive distillation to make ethylene glycol from EO and water. Such process are described in Podrebarac et al., "More used for catalytic distillation," CHEMTECH, May, pages 37-45 (1997); Ciric et al., "Steady state multiplicities in an ethylene glycol reactive distillation column," Ind. Eng. Chem. Res., 33(11), pages 2738-2748 (1994); Ciric et al., "Synthesis of nonequilibrium reactive distillation processes by MINLP optimization," AIChE Journal, 40(9), pages 1479-1487 (1994). Heretofore, reactive distillation has not be used for the production of alkanolamines.